In a conventional hemming device incorporating state-of-art technology, the hemming stroke and the required hemming force are applied through a hydraulic cylinder lying centrally under the ram. The ram with the superposed hemming conveys the sheet material to be hemmed against the stationary pre-hemming and/or finishing tools which are affixed to slideable or swingable devices, such as described in U.S. Pat. No. 5,150,508, and DE 43 30 683 C2, and hereby incorporated by reference. Owing to the central introduction of forces in the center of the ram, the ram as a whole must be of a very stable construction in order to be capable of transferring the hemming force from the center to particularly the edge zone of the ram.